The present invention relates to a pigmented paint formulation containing a phosphorus acid functionalized latex binder and an associative thickener that is designed to give formulators flexibility in targeting a desired Stormer (KU) viscosity of the composition, particularly when elevated ICI viscosity is desired.
Titanium dioxide (TiO2) is widely used to create opacity in paint formulations due to its high index of refraction. The rapid rise in the cost in TiO2 has led to the search for more efficient ways to reduce concentrations of this pigment without sacrificing hiding. Efficiency can be achieved by improving the spacing between TiO2 particles, for example, by adsorbing phosphorus acid functionalized emulsion polymer particles to the surfaces of the TiO2 particles. (See, for example, U.S. Pat. Nos. 7,081,488, 7,179,531, and US 2015/000546 A1). The resulting composite structures exhibit an increase in viscosity efficiency, which may adversely affect a formulator's ability to tailor the KU rheological response to a desired viscosity using a traditional thickener such as a hydrophobically modified ethylene oxide urethane (HEUR) polymer thickener. This consequence appears to be especially acute where the adsorbing polymer particles exhibit a so-called acorn morphology, where the adsorbing portion of the particle is confined to a small protuberance off the surface of a larger spherical particle.
It would therefore be desirable to discover a composition that provides both efficient use TiO2 and KU building capability. Such a composition would facilitate viscosity adjustment of a paint formulation at high shear rates in the presence of composite particles without exceeding viscosity targets at low and mid shear rates, and would have the added benefit of increased flexibility in the use of low and mid shear rate thickeners to balance other paint performance properties.